The invention relates to three-position control apparatus for electrical switchgear and itself controlled by means of a rotary shaft, and in particular for an electrical power station switch. More particularly, it relates to apparatus for causing switchgear to go from one position to another in determined manner, either automatically by means of an electrical command from a central control unit, or optionally manually by means of a crank handle, in the event of a power failure and in particular a failure at the central control unit.
Such apparatus serves to remove the possibility of the switchgear going from one position to another without a command being given to that effect, as well as the possibility of the switchgear going from one position to another without following a given sequence, e.g. going from a first position to a third position without going through the second position which is required as being a necessary intermediate position.
For reasons of staff safety and/or of protecting equipment, it is often necessary to require a determined sequence for going from one position to another so as to satisfy given conditions, e.g. so as to avoid untimely grounding of a link that is live.
For example, such conditions are imposed for apparatus serving to control a generator circuit in a facility for generating electrical power. In such a facility, the apparatus makes it possible either to cause an interconnection to be established between the generator and a grid transformer by closing a disconnector, or to cause such an interconnection to be interrupted by opening the disconnector, or else to cause grounding to take place, with the disconnector open.
The invention thus provides control apparatus for controlling electrical switchgear by rotating a control shaft, to go only from a determined angular position to one of a plurality of other determined angular positions, under the action of electrically or mechanically controlled drive mechanism.